post data to MVC Controller from view using Ajax.

Question

 

i am using ajax for 4 years , but seriously i couldn't understand it completely when it comes to post data to controller.

for me its pure luck, sometimes some method works sometimes something other and sometimes nothing works.

I have below example

 

Approach 1. Failed here(though it works sometimes,idk why)

$("#btnInsert").click(function () {
        debugger;



        var employee = {
            Name: $("#txtName1").val(), // have value
            Salary: $("#txtSalary1").val(), // have value
        }

        $.ajax({
            type: "POST",
            url: '/employee/AddEmployees',
            data: JSON.stringify(employee), // have values
            datatype: "json",
            cache: false,
            success: function (data) {

            },
        });

    });

 public ActionResult AddEmployees(Employee employee) // values are null
        {
            try
            {
                if (ModelState.IsValid)
                {

                    var azuS = client.PostAsJsonAsync("api/Employee", employee).Result;
                    if (azuS.IsSuccessStatusCode)
                    {
                        return Json(employee, JsonRequestBehavior.AllowGet);
                    }

                }
                return RedirectToAction("GetAllEmployee", "Employee");
            }
            catch (Exception ex)
            {
                return Json(ex.Message);
            }
        }

 second approach :- failed. (worked 70% times earlier)

 

$("#btnInsert").click(function () {
        debugger;



        var employee = {
            Name: $("#txtName1").val(), // have value
            Salary: $("#txtSalary1").val(), // have value
        }
        var model={
         "emp":employee
          }
        $.ajax({
            type: "POST",
            url: '/employee/AddEmployees',
            data:model, // have values
            datatype: "json",
            cache: false,
            success: function (data) {

            },
        });

    });

 public ActionResult AddEmployees(Employee emp) // values are null
        {
            try
            {
                if (ModelState.IsValid)
                {

                    var azuS = client.PostAsJsonAsync("api/Employee", employee).Result;
                    if (azuS.IsSuccessStatusCode)
                    {
                        return Json(employee, JsonRequestBehavior.AllowGet);
                    }

                }
                return RedirectToAction("GetAllEmployee", "Employee");
            }
            catch (Exception ex)
            {
                return Json(ex.Message);
            }
        }

 Approach 3:- query string (no data, directly construct url) (Success here)

$.ajax({
            type: "POST",
            url: '/employee/AddEmployees?Name='+employee.Name+"Salary="+employee.Salary,

            datatype: "json",
            cache: false,
            success: function (data) {

            },
        });

 what is wrong with method 1 and 2.

Yes i tried with contentType:application/json;charset:utf-8;

 please tell me a way which works in every situation no matter what.